Semiconductor devices having through-stack interconnects for facilitating connectivity testing

ABSTRACT

Semiconductor devices having through-stack interconnects for facilitating connectivity testing, and associated systems and methods, are disclosed herein. In one embodiment, a semiconductor device includes a stack of semiconductor dies and a plurality of through-stack interconnects extending through the stack to electrically couple the semiconductor dies. The interconnects include functional interconnects and at least one test interconnect. The test interconnect is positioned in a portion of the stack more prone to connectivity defects than the functional interconnects. Accordingly, testing the connectivity of the test interconnect can provide an indication of the connectivity of the functional interconnects.

TECHNICAL FIELD

The present disclosure generally relates to semiconductor devices having through-stack interconnects, and more particularly relates to semiconductor devices having dedicated through-stack interconnects extending through areas prone to warpage for facilitating connectivity testing.

BACKGROUND

Packaged semiconductor dies, including memory chips, microprocessor chips, and imager chips, typically include one or more semiconductor dies mounted on a substrate and encased in a protective covering. The semiconductor dies include functional features, such as memory cells, processor circuits, and imager devices, as well as bond pads electrically connected to the functional features. The bond pads can be electrically connected to terminals outside the protective covering to allow the semiconductor die to be connected to higher level circuitry. Within some packages, semiconductor dies can be stacked upon and electrically connected to one another by individual interconnects placed between adjacent semiconductor dies. In such packages, each interconnect can include a conductive material (e.g., solder) and a pair of contacts on opposing surfaces of adjacent semiconductor dies. For example, a metal solder can be placed between the contacts and reflowed to form a conductive joint.

One challenge with such traditional packages is that variations in heat and/or force can exist during a bonding operation to form the interconnects. This can affect the quality of the interconnects, for example, by leading to an open-circuit across the solder joints, high ohmic resistance across the solder joints, solder bridging between nearby interconnects, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present technology can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Instead, emphasis is placed on illustrating clearly the principles of the present technology.

FIG. 1 is a side cross-sectional view of a semiconductor device in accordance with an embodiment of the present technology.

FIG. 2 is a partially schematic, enlarged side cross-sectional view of a test interconnect of the semiconductor device of FIG. 1 configured in accordance with an embodiment of the present technology.

FIG. 3 is a flow diagram of a process or method for determining the connectivity of a test interconnect within a semiconductor device configured in accordance with an embodiment of the present technology.

FIG. 4 is a table of logic states corresponding to the connectivity of the test interconnect of FIG. 2 as determined by the method of FIG. 3, in accordance with an embodiment of the present technology.

FIG. 5 is a flow diagram of a process or method for determining the connectivity of through-stack interconnects of a semiconductor device configured in accordance with an embodiment of the present technology.

FIG. 6 is a top view of a semiconductor device in accordance with an embodiment of the present technology.

FIG. 7 is a schematic view of a system that includes a semiconductor device configured in accordance with embodiments of the present technology.

DETAILED DESCRIPTION

Specific details of several embodiments of semiconductor devices having dedicated through-stack interconnects for testing the connectivity of other, functional through-stack interconnects, and associated systems and methods, are described below. In several of the embodiments described below, a method for testing the connectivity of through-stack interconnects extending through a stack of semiconductor dies includes (i) determining the connectivity of a test through-stack interconnect extending through a first portion of the stack and, (ii) based on the determined connectivity of the test through-stack interconnect, determining the connectivity of a plurality of functional through-stack interconnects extending through a second portion of the stack. In some embodiments, the second portion of the stack is less prone to connectivity defects than the first portion of the stack. For example, the first portion of the stack can be a laterally outboard portion of the stack that is adjacent to one or more edges of the stack, and that is more susceptible to bending or warpage during a bonding operation used to form the through-stack interconnects. Accordingly, it can be determined that the functional through-stack interconnects are likely connected if the test through-stack interconnect—positioned in a more high-risk region of the stack—is determined to be connected. Thus, the present technology can advantageously facilitate connectivity testing of the through-stack interconnects in a semiconductor device without requiring that each interconnect be tested individually.

As used herein, the terms “vertical,” “lateral,” “upper,” and “lower” can refer to relative directions or positions of features in the semiconductor devices in view of the orientation shown in the Figures. For example, “upper” or “uppermost” can refer to a feature positioned closer to the top of a page than another feature. These terms, however, should be construed broadly to include semiconductor devices having other orientations, such as inverted or inclined orientations where top/bottom, over/under, above/below, up/down, and left/right can be interchanged depending on the orientation.

Unless the context indicates otherwise, structures disclosed herein can be formed using conventional semiconductor-manufacturing techniques, and stages of the methods used to form the structures can be performed at the wafer level or at the die level. Materials can be deposited, for example, using chemical vapor deposition, physical vapor deposition, atomic layer deposition, spin coating, and/or other suitable techniques. Similarly, materials can be removed, for example, using plasma etching, wet etching, chemical-mechanical planarization, or other suitable techniques. A person skilled in the relevant art will also understand that the technology may have additional embodiments, and that the technology may be practiced without several of the details of the embodiments described below with reference to FIGS. 1-7.

FIG. 1 is a side cross-sectional view of a semiconductor device 100 (“device 100”) configured in accordance with an embodiment of the present technology. The device 100 includes a plurality of semiconductor dies 102 (individually labeled as first through fourth semiconductor dies 102 a-d) arranged in a stack 105. Each of the semiconductor dies 102 can have integrated circuitry IC including one or more of, for example, a memory circuit (e.g., a dynamic random memory (DRAM)), a controller circuit (e.g., a DRAM controller), a logic circuit, a detection circuit (as described in greater detail below with reference to FIG. 2), and/or other circuits. In some embodiments, each of the semiconductor dies 102 can include similar components and/or have similar configurations. For example, the semiconductor dies 102 can be identical (e.g., including identical components). In certain embodiments, one or more of the semiconductor dies 102 can be configured as a master and the other semiconductor dies 102 can be configured as slaves of the master. In some embodiments, the stack 105 can include more or fewer than the illustrated four semiconductor dies 102 (e.g., two semiconductor dies, three semiconductor dies, or five or more semiconductor dies).

The device 100 also includes a plurality of through-stack interconnects 110 (“interconnects 110”) extending generally vertically through the stack 105 and electrically coupling the semiconductor dies 102. More particularly, the device 100 includes an array of individual first through-stack interconnects 110 a (“first interconnects 110 a”) that extend through a first portion 108 a of the stack 105, a second through-stack interconnect 110 b that extends through a second portion 108 b of the stack 105, and a third through-stack interconnect 110 c that extends through a third portion 108 c of the stack 105. Each of the interconnects 110 can be composed of a combination of vertically and/or laterally arranged conductive elements interconnected to one another throughout the stack 105 of semiconductor dies 102. For example, each of the interconnects 110 can include an arrangement of interconnected through-die vias 112, conductive pillars 114, solder bumps 116, conductive pads 118, and/or other suitable conductive elements such as metal traces, etc. The interconnects 110 can be formed by a suitable bonding operation, or other process as is well known in the art.

The first interconnects 110 a can be functional through-stack interconnects (e.g., signal lines and power lines) that are used during operation of the device 100. In some embodiments, the device 100 can include a smaller or greater number of first interconnects 110 a than shown in FIG. 1. For example, the device 100 can include tens, hundreds, thousands, or more first interconnects 110 a extending through the stack 105 of semiconductor dies 102. As described in detail below with reference to FIGS. 2-5, the interconnects 110 b, c can be test interconnects configured for use during a connectivity test to determine the connectivity of the first interconnects 110 a. Accordingly, the interconnects 110 b, c can be referred to herein as test interconnects 110 b, c. In other embodiments, more than test interconnect 110 b can be formed in the second portion 108 b of the stack 105, more than one test interconnect 110 c can be formed in the third portion 108 c of the stack 105, and/or the device 100 could include only the test interconnect(s) 110 b or the test interconnect(s) 110 c.

The portions 108 b, c of the stack 105 can be portions of the stack 105 in which interconnects formed therein are more prone to connectivity defects than identical interconnects formed in the first portion 108 a of the stack. That is, the test interconnects 110 b, c are positioned in a region of the stack 105 such that they are more likely to be electrically disconnected or otherwise compromised from errors or variations in the bonding operation used to form the interconnects 110. In the illustrated embodiment, for example, the portions 108 b, c are positioned laterally outboard of the first portion 108 a and adjacent to opposing first and second edges 107 a, b, respectively, of the stack 105. As such, the portions 108 b, c can be more prone to warpage (e.g., bending, deformation, etc.) during the bonding operation used to form the interconnects 110, which can damage interconnects formed therein. In some embodiments, the first portion 108 a can have a width W₁ of between about 5000-1000 μm (e.g., about 6000 μm, about 9000 μm, etc.) and the portions 108 b, c can have widths W₂ and W₃, respectively, of between about 50-250 μm (e.g., about 200 μm). In some embodiments, the test interconnects 110 b, c can be formed a distance of between about 50-150 μm (e.g., about 100 μm) from the edges 107 a, b, respectively, of the stack 105. Accordingly, in some embodiments, the test interconnects 110 b, c can be positioned nearer to an edge of the stack 105 than any one of the first interconnects 110 a.

In general, because the test interconnects 110 b, c are formed in a portion of the stack 105 that is more prone to damage during the bonding operation used to form the interconnects 110 (e.g., closer to a lateral edge of the stack, closer to a corner of the stack, closer to an aperture through the stack, etc.), a determined connectivity of the test interconnects 110 b, c can serve as an indication of (e.g., proxy for) the connectivity of the first interconnects 110 a. That is, if the test interconnects 110 b, c are electrically connected, the first interconnects 110 a—positioned in a less defect prone portion of the stack 105—are likely connected as well. Conversely, if the test interconnects 110 b, c are electrically disconnected, it is more likely that at least one of the first interconnects 110 a is also electrically disconnected.

In some embodiments, the device 100 can further include other structures or features such as, for example: (i) a casing (e.g., a thermally conductive casing that encloses the semiconductor dies 102 within an enclosure), (ii) an underfill material deposited or otherwise formed around and/or between the semiconductor dies 102, and/or (iii) a support substrate (e.g., an interposer and/or a printed circuit board configured to operably couple the semiconductor dies 102 to external circuitry).

FIG. 2 is a partially schematic, enlarged side cross-sectional view of the test interconnect 110 b of the device 100 configured in accordance with an embodiment of the present technology. In the illustrated embodiment, the fourth semiconductor die 102 d is shown warped relative to the third semiconductor die 102 c to illustrate various aspects of the present technology. The warpage could be the result of, for example, variations in heat and/or force during the bonding operation used to from the interconnects 110, and can cause a connectivity defect in the test interconnect 110 b such as the illustrated electrical disconnection (e.g., open circuit) between the solder bump 116 on the conductive pillar 114 of the fourth semiconductor die 102 d, and the conductive pad 118 on the third semiconductor die 102 c. In some instances, the connectivity defect can be a partial electrical disconnection (e.g., a highly resistive connection) or other type of connectivity defect. In general, one or more of the semiconductor dies 102 could be warped and/or one or more connectivity defects could exist along the interconnect 110 b.

In the illustrated embodiment, the integrated circuitry IC (FIG. 1) of each of the semiconductor dies 102 a-d includes a detection circuit DC₁-DC₄, respectively. The detection circuits DC₁-DC₄ are electrically coupled to the test interconnect 110 b (and/or the test interconnect 110 c). In some embodiments, the detection circuits DC₁-DC₄ are not electrically coupled to the first interconnects 110 a. In general, the detection circuits DC₁-DC₄ can be configured to (i) output a signal to the test interconnect 110 b, (ii) detect a signal carried by the test interconnect 110 b, and/or (iii) output a logic signal indicative of a resistance (e.g., connectivity) of the test interconnect 110 b. More particularly, in some embodiments, the first semiconductor die 102 a can be configured as a master while the semiconductor dies 102 b-d can be configured as slaves of the first, master semiconductor die 102 a. In such embodiments, the detection circuit DC₁ of the first semiconductor die 102 a can include a signal source (e.g., a p-channel) configured to output a signal SIGNAL_P to the test interconnect 110 b. The detection circuit DC₁ can also receive a signal SIGNAL_OUT from the test interconnect 110 b (e.g., a resultant voltage of the test interconnect 110 b), and output (e.g., to an output buffer or data terminal of the device 100) a logic signal LOGIC_OUT based on the received signal SIGNAL_OUT.

The detection circuits DC₂-DC₄ of the slave semiconductor dies 102 b-d can each include signal sources (e.g., n-channels) configured to output signals SIGNAL_N₁-N₃, respectively, to the test interconnect 110 b. In some embodiments, the signals SIGNAL_N₁-N₃ are n-channel pulldown signals having a n-ch drive strength (e.g., a first drive strength), and the signal SIGNAL_P is a p-channel pullup signal having a p-ch drive strength (e.g., a second drive strength), less than the n-ch drive strength. In certain embodiments, for example, the p-ch drive strength can about ten times greater or about twenty times greater than the n-ch drive strength. In other embodiments, the signals generated by the detection circuits DC₂-DC₄ be other suitable signals generated by different signal sources and having different relative drive strengths. Although the first semiconductor die 102 a is referred to as the master in the embodiment of FIG. 2, in other embodiments, any one of the semiconductor dies 102 can be configured as the master. In yet other embodiments, the semiconductor dies 102 can have arrangements other than master-slave.

As described in greater detail below with reference to FIGS. 3 and 4, the signals SIGNAL_N₁-N₃ and the signal SIGNAL_P can be selectively toggled on and off as part of a connectivity test to determine a resistance of and therefore connectivity of the test interconnect 110 b. For example, the signals SIGNAL_N₁-N₃ can be individually toggled on (e.g., pull-down can be enabled on the semiconductor dies 102 b-d) at the same time as the signal SIGNAL_P is toggled on (e.g., pull-up enabled on the first semiconductor die 102 a). In general, the signal SIGNAL_OUT will vary depending on the resistance of the test interconnect 110 b between the first semiconductor die 102 a and the enabled one of the semiconductor dies 102 b-d. For example, if the test interconnect 110 b is highly resistive or electrically disconnected therebetween, the SIGNAL_OUT at the first semiconductor die 102 a is dominated (e.g., substantially determined) by the smaller drive strength of the signal SIGNAL_P from the master semiconductor die 102 a. Contrariwise, if the test interconnect 110 b is well connected therebetween, the signal SIGNAL_OUT at the first semiconductor die 102 a is dominated by the greater drive strength of the signals SIGNAL_N₁-N₃ from the toggled one of the semiconductor dies 102 b-d.

The detection circuit DC₁ of the master semiconductor die 102 a can be configured to compare the signal SIGNAL_OUT to a threshold magnitude, and the comparison can drive the logic signal LOGIC_OUT high or low. For example, if the test interconnect 110 b is highly resistive or electrically disconnected (e.g., the signal SIGNAL_OUT is dominated by the signal SIGNAL_P such that the SIGNAL_OUT is below the threshold magnitude), then the logic signal LOGIC_OUT can have a first state (e.g., a high state). If the test interconnect 110 b is electrically connected (e.g., the signal SIGNAL_OUT is dominated by the toggled one of the signals SIGNAL_N₁-N₃ such that the signal SIGNAL_OUT is above the threshold magnitude), then the logic signal LOGIC_OUT can have a second state (e.g., a high state). In this manner, the logic signal LOGIC_OUT can provide an indication of the connectivity of the test interconnect 110 b between the first semiconductor die 102 a and the toggled one of the semiconductor dies 102 b-d.

More specifically, FIG. 3 is a flow diagram of a process or method 330 for determining the connectivity of a test interconnect within a semiconductor device configured in accordance with an embodiment of the present technology. For the sake of illustration, some features of the method 330 are described in the context of the embodiment shown in FIG. 2. FIG. 4 is a table illustrating the toggling of the signals SIGNAL_N₁-N₃ and the signal SIGNAL_P, and the resulting logic states of the logic signal LOGIC_OUT for each stage of the method 330 in the context of the embodiment shown in FIG. 2.

Referring to FIG. 3, beginning at block 332, the method 330 includes testing the connectivity of the test interconnect 110 b between the first semiconductor die 102 a and the second semiconductor die 102 b. For example, as illustrated in FIG. 4, both the signal SIGNAL_P and the signal SIGNAL_N₁ can be toggled on, while the signals SIGNAL_N₁, N₂ are toggled off. Because the test interconnect 110 b is electrically connected between the semiconductor dies 102 a, b, the signal SIGNAL_OUT at the first semiconductor die 102 a is dominated by the greater drive strength of the signal SIGNAL_N₁, which drives the logic signal LOGIC_OUT to the low state.

At block 334, the method 330 includes testing the connectivity of the test interconnect 110 b between the first semiconductor die 102 a and the third semiconductor die 102 c. For example, as illustrated in FIG. 4, both the signal SIGNAL_P and the signal SIGNAL_N₂ can be toggled on, while the signals SIGNAL_N₁, N₃ are toggled off. Because the test interconnect 110 b is electrically connected between the semiconductor dies 102 a, c, the signal SIGNAL_OUT at the first semiconductor die 102 a is dominated by the greater drive strength of the signal SIGNAL_N₂, which drives the logic signal LOGIC_OUT to the low state.

At block 336, the method 330 includes testing the connectivity of the test interconnect 110 b between the first semiconductor die 102 a and the fourth semiconductor die 102 d. For example, as illustrated in FIG. 4, both the signal SIGNAL_P and the signal SIGNAL_N₃ can be toggled on, while the signals SIGNAL_N₁, N₂ are toggled off. Because the test interconnect 110 b is electrically disconnected between the semiconductor dies 102 a, d, the signal SIGNAL_OUT at the first semiconductor die 102 a is dominated by the smaller drive strength of the signal SIGNAL_P, which drives the logic signal LOGIC_OUT to the high state.

The logic signal LOGIC_OUT can be read out of the device 100 to provide an indication of the connectivity of the test interconnect 110 b. Based on the logic signal LOGIC_OUT having a high state (block 336), it can be determined that the test interconnect 110 b is not well connected. In some embodiments, by testing the connectivity between each pair of semiconductor dies 102 in the stack 105, the specific position of the connectivity defect can be determined. For example, because the logic signal LOGIC_OUT is in the low state for each of the tests between the semiconductor dies 102 a-c (blocks 332 and 334), it can be determined that the test interconnect 110 b is disconnected between the semiconductor dies 102 c, d. In other embodiments, the method 330 need not include testing the electrical connectivity between each pair of semiconductor dies 102 in the stack 105. For example, the method 330 can include testing only the connectivity between the uppermost and lowermost semiconductor dies 102 in the stack 105 (block 336), or another single pair of semiconductor dies 102 in the stack 105. Alternatively, the method 330 could terminate after a connectivity issue is detected between any pair of semiconductor dies 102 in the stack 105.

In some embodiments, instead of or in addition to reading out the logic signal LOGIC_OUT, the signal SIGNAL_OUT can be read out of the device 100 to, for example, provide information about a degree to which the test interconnect 110 b is connected. For example, the voltage level of the signal SIGNAL_OUT can indicate whether the test interconnect 110 b is completely disconnected, or only partially disconnected but highly resistive. In still other embodiments, the strength of one or more of the signals SIGNAL_N₁-N₃ and the signal SIGNAL_P can be varied to enable more detailed or specific testing and determination of the resistance of the test interconnect 110 b. In particular, the ratio of the n-ch and p-ch drive strengths can be changed by changing the total drive of the transistors by adding more transistor width.

The device 100 can be configured for performing a connectivity test of the test interconnect 110 c (FIG. 1) in a substantially similar or the same manner as the test interconnect 110 b, as described in detail above with reference to FIGS. 2-4.

FIG. 5 is a flow diagram of a process or method 540 for determining the connectivity of the first interconnects 110 a of the device 100 (FIG. 1) configured in accordance with an embodiment of the present technology. Beginning at block 542, the method 540 includes determining the resistance of at least one test through-stack interconnect between at least two semiconductor dies 102 in the stack 105. For example, as set forth in detail above with reference to FIG. 3, the method 330 can be employed to read out a logic signal (e.g., the signal LOGIC_OUT) indicative of the resistance of the test interconnects 110 b, c between one or more pairs of the semiconductor dies 102 in the stack 105. In some embodiments, the method 540 can include determining the resistance of both of the test interconnects 110 b, c. In other embodiments, the method 540 can include determining the resistance of only one of the test interconnects 110 b, c, and/or determining the resistance of additional test interconnects (not pictured) of the device 100 that are also formed in at-risk portions of the stack 105.

At block 544, the method 540 includes comparing the resistances of the test interconnects 110 b, c to a threshold value. For example, as set forth in detail above with reference to FIG. 3, comparing the resistances to the threshold value can include determining or reading the state (e.g., high or low) of the logic signal output from the device 100. In other embodiments, comparing the resistances to the threshold value can include directly comparing the resistances (e.g., the magnitude of the signal SIGNAL_OUT) to the threshold value.

The method 540 branches depending on the result of the comparison at block 544. In some embodiments, if the resistances of the test interconnects 110 b, c are each below the threshold value, the method 540 proceeds to block 546 where a determination is made that the first interconnects 110 a are electrically connected, or at least that substantially all of the first interconnects 110 a are electrically connected. In particular, because the test interconnects 110 b, c are formed in a more at-risk portion of the stack 105, if the test interconnects 110 b, c are each electrically connected, the first interconnects 110 a—positioned in a less defect prone portion of the stack 105—are also likely electrically connected. In the embodiment illustrated in FIG. 1, the soundness of the determination is bolstered because the test interconnects 110 b, c are positioned proximate the opposing edges 107 a, b of the stack 105. Thus, the electrical connectivity of both test interconnects 110 b, c can indicate that the device 100 is relatively planar between the opposing edges 107 a, 107 b. In some embodiments, where the resistance of multiple test interconnects is determined, the method 540 can proceed to block 546 even if one or more of the multiple test interconnects are determined to be highly resistive.

In some embodiments, if at least one of the resistances of the test interconnects 110 b, c is above the threshold value, the method 540 proceeds to block 548 where a determination is made that at least a portion of the first interconnects 110 a are electrically disconnected. In particular, if at least one of the test interconnects 110 b, c is electrically disconnected, it is more likely that at least one of the first interconnects 110 a is also electrically disconnected. Disconnected or highly resistive ones of the first interconnects 110 a can render the device 100 inoperable. In some embodiments, where the resistance of multiple test interconnects is determined, the method 540 can proceed to block 548 only if two or more of the multiple test interconnects (e.g., those on opposing sides of the device 100) are determined to be highly resistive.

Accordingly, the present technology advantageously allows for robust connectivity testing of the first interconnects 110 a of the device 100 without requiring that the connectivity of each individual first interconnect 110 a be tested—which can be costly and time-consuming. Rather, the present technology monitors the connectivity of only a limited number of at-risk test interconnects 110 b, c, thereby reducing the time needed to test and verify that the first interconnects 110 a are connected. In addition, the present technology reduces or eliminates the need for complex circuitry and test methods otherwise necessary to test each individual first interconnect 110 a. Moreover, the test interconnects 110 b, c can be formed in at-risk portions of the device 100 that would not otherwise include the functional first interconnects 110 a. As such, the test interconnects 110 b, c do not occupy an area that would otherwise be used for functional features and can be included in the device 100 without increasing the size of the device 100 and/or decreasing the signal density in the device 100.

While many of the embodiments described above include two test interconnects positioned proximate opposing edges of a semiconductor device, one skilled in the art will understand that the semiconductor devices of the present technology can include any number of test interconnects having any suitable positioning. In some embodiments, the number and positioning of test interconnects can be based on the specific layout of the functional interconnects within a semiconductor device. For example, FIG. 6 is a schematic top view of a semiconductor device 600 configured in accordance with an embodiment of the present technology. The semiconductor device 600 can include features generally similar to the features of the semiconductor device 100 described in detail above. For example, the semiconductor device 600 includes a plurality semiconductor dies 602 (only an uppermost semiconductor die 602 is visible in FIG. 6) arranged in a stack, and through-stack interconnects 610 (shown schematically) extending through the stack to electrically couple the semiconductor dies 602. The through-stack interconnects can include functional interconnects 610 a and test interconnects 610 b.

In the illustrated embodiment, the semiconductor dies 602 are generally rectilinear and the stack of semiconductor dies 602 includes a central portion 652 and a peripheral portion 654. The functional through-stack interconnects 610 a extend through the central portion 652, while the test interconnects 610 b extend through the peripheral portion 654. As described in detail above, the test interconnects 610 b can be more prone to connectivity defects because, for example, the peripheral portion 654 is more likely to be damaged (e.g., warped) by a bonding operation used to form the through-stack interconnects 610. The test interconnects 610 b are generally evenly spaced in the peripheral portion 654 around the functional interconnects 610 a. Accordingly, connectivity testing of the test interconnects 610 b can provide a robust determination of the connectivity of the functional through-stack interconnects 610 a—which are generally evenly positioned throughout the central portion 652 of the stack. For example, a determination that each of the test interconnects 610 b is connected can provide a strong indication that the semiconductor device 600 is relatively planar, and thus that functional interconnects 610 a are likely electrically connected.

Any one of the semiconductor devices having the features described above (e.g., with reference to FIGS. 1-6) can be incorporated into any of a myriad of larger and/or more complex systems, a representative example of which is system 790 shown schematically in FIG. 7. The system 790 can include a processor 792, a memory 794 (e.g., SRAM, DRAM, flash, and/or other memory devices), input/output (I/O) devices 796, and/or other subsystems or components 798. The semiconductor dies and semiconductor die assemblies described above can be included in any of the elements shown in FIG. 5. The resulting system 790 can be configured to perform any of a wide variety of suitable computing, processing, storage, sensing, imaging, and/or other functions. Accordingly, representative examples of the system 790 include, without limitation, computers and/or other data processors, such as desktop computers, laptop computers, Internet appliances, hand-held devices (e.g., palm-top computers, wearable computers, cellular or mobile phones, personal digital assistants, music players, etc.), tablets, multi-processor systems, processor-based or programmable consumer electronics, network computers, and minicomputers. Additional representative examples of the system 790 include lights, cameras, vehicles, etc. With regard to these and other example, the system 790 can be housed in a single unit or distributed over multiple interconnected units, e.g., through a communication network. The components of the system 790 can accordingly include local and/or remote memory storage devices and any of a wide variety of suitable computer-readable media.

The above detailed descriptions of embodiments of the technology are not intended to be exhaustive or to limit the technology to the precise form disclosed above. Although specific embodiments of, and examples for, the technology are described above for illustrative purposes, various equivalent modifications are possible within the scope of the technology, as those skilled in the relevant art will recognize. For example, while steps or stages are presented in a given order, alternative embodiments may perform steps in a different order. Moreover, the various embodiments described herein may also be combined to provide further embodiments. Reference herein to “one embodiment,” “an embodiment,” or similar formulations means that a particular feature, structure, operation, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present technology. Thus, the appearances of such phrases or formulations herein are not necessarily all referring to the same embodiment.

Certain aspects of the present technology may take the form of computer-executable instructions, including routines executed by a controller or other data processor. In some embodiments, a controller or other data processor is specifically programmed, configured, and/or constructed to perform one or more of these computer-executable instructions. Furthermore, some aspects of the present technology may take the form of data (e.g., non-transitory data) stored or distributed on computer-readable media, including magnetic or optically readable and/or removable computer discs as well as media distributed electronically over networks. Accordingly, data structures and transmissions of data particular to aspects of the present technology are encompassed within the scope of the present technology. The present technology also encompasses methods of both programming computer-readable media to perform particular steps and executing the steps.

Moreover, unless the word “or” is expressly limited to mean only a single item exclusive from the other items in reference to a list of two or more items, then the use of “or” in such a list is to be interpreted as including (a) any single item in the list, (b) all of the items in the list, or (c) any combination of the items in the list. Where the context permits, singular or plural terms may also include the plural or singular term, respectively. Additionally, the term “comprising” is used throughout to mean including at least the recited feature(s) such that any greater number of the same feature and/or additional types of other features are not precluded. Further, while advantages associated with certain embodiments of the technology have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the technology. Accordingly, the disclosure and associated technology can encompass other embodiments not expressly shown or described herein. 

We claim:
 1. A method for testing a stack of semiconductor dies, the method comprising: determining a resistance of a first through-stack interconnect extending through a first portion of the stack of semiconductor dies; and based on the determined resistance, determining a connectivity of a plurality of second through-stack interconnects extending through a second portion of the stack of semiconductor dies, wherein the second portion of the stack of semiconductor dies is less prone to connectivity defects than the first portion of the stack of semiconductor dies.
 2. The method of claim 1, wherein the first portion of the stack of semiconductor dies is laterally outboard of the second portion.
 3. The method of claim 1, wherein determining the resistance of the first through-stack interconnect includes determining a logic state of a signal output by a detection circuit of one of the semiconductor dies in the stack of semiconductor dies.
 4. The method of claim 3, wherein determining the connectivity of the plurality of second through-stack interconnects includes: when the logic state is a first logic state, determining that all of the plurality of second through stack interconnects are electrically connected; and when the logic state is a second logic state, determining that at least a portion of the plurality of second through stack interconnects are electrically disconnected.
 5. The method of claim 1, wherein determining the connectivity of the plurality of second through-stack interconnects is performed without passing current through any of the plurality of plurality of second through-stack interconnects.
 6. The method of claim 1, wherein determining the resistance of the first through-stack interconnect includes: enabling a first signal source on a first semiconductor die in the stack of semiconductor dies, the first signal source electrically connected to the first through-stack interconnect; enabling a second signal source on a second semiconductor die in the stack of semiconductor dies, the second signal source electrically connected to the first through-stack interconnect; and determining the resistance of the first through-stack interconnect based on an output signal of the first through-stack interconnect detected at the first semiconductor die in the stack of semiconductor dies.
 7. The method of claim 6, wherein the first signal source is a p-channel of the first semiconductor die configured to produce a first drive strength, wherein the second signal source is an n-channel of the second semiconductor die configured to produce a second drive strength, and wherein the second drive strength is at least twice as great as the first drive strength.
 8. The method of claim 6, wherein when the resistance is above a threshold magnitude, the output signal is determined by a first signal produced by the first signal source; and when the resistance is below the threshold magnitude, the output signal is determined by a second signal produced by the second signal source.
 9. The method of claim 1, further comprising determining a resistance of a third through-stack interconnect extending through a third portion of the stack of semiconductor dies, wherein determining the connectivity of the plurality of second through-stack interconnects is based on the determined resistances of the first through-stack interconnect and the determined resistance of the third through-stack interconnects; and the second portion of the stack of semiconductor dies is less prone to the connectivity defects than the third portion of the stack of semiconductor dies.
 10. The method of claim 9, wherein the first portion of the stack of semiconductor dies is adjacent to a first edge of the stack of semiconductor dies; the second portion of the stack of semiconductor dies is adjacent to a second edge of the stack of semiconductor dies, opposite the first edge; and the third portion of the stack of semiconductor dies is laterally between the first portion and the second portions.
 11. A method for testing a stack of semiconductor dies, the method comprising: providing a first signal having a first drive strength to a test through-stack interconnect from a first semiconductor die in the stack of semiconductor dies; providing a second signal having a second drive strength to the test through-stack interconnect from a second semiconductor die in the stack of semiconductor dies; receiving a signal indicative of a resultant voltage of the test through-stack interconnect, the resultant voltage determined at the first semiconductor die; when the signal indicative of the resultant voltage has a first state, determining that all of a plurality of functional through-stack interconnects are electrically connected, the plurality of functional through-stack interconnects extending through the stack of semiconductor dies; and when the signal indicative of the resultant voltage has a second state, determining that at least one of the plurality of functional through-stack interconnects other than the test through-stack interconnect is electrically disconnected.
 12. The method of claim 11, wherein the first signal is a p-channel pullup signal, wherein the second voltage is an n-channel pulldown signal, and wherein the first drive strength is greater than the second drive strength.
 13. The method of claim 11, wherein when a resistance of the test through-stack interconnect is below a threshold magnitude, the signal indicative of the resultant voltage has the first state; and when the resistance of the test through-stack interconnect is above a threshold magnitude, the signal indicative of the resultant voltage has the second state.
 14. The method of claim 11, wherein the first drive strength is variable.
 15. The method of claim 11, wherein the signal indicative of the resultant voltage is a first signal indicative of the resultant voltage, and wherein the method further comprises: while providing the first signal and after providing the second signal to the test through-stack interconnect, providing a third signal having a third drive strength to the test through-stack interconnect from a third semiconductor die in the stack of semiconductor dies; receiving a second signal indicative of another resultant voltage of the test through-stack interconnect, the other resultant voltage determined at the first semiconductor die in the stack of semiconductor dies; when the first signal indicative of the resultant voltage and the second signal indicative of the other resultant voltage have the same first state, determining that all of the functional through-stack interconnects are electrically connected; and when at least one of the first signal indicative of the resultant voltage and the second signal indicative of the other resultant voltage have the second state, determining that at least one of the functional through-stack interconnects other than the test through-stack interconnect is electrically disconnected.
 16. The method of claim 11, wherein the test through-stack interconnect is located laterally nearer to an edge of the stack of semiconductor dies than any of the functional through-stack interconnects.
 17. A method for testing a stack of semiconductor dies, the method comprising: determining resistances of a first through-stack interconnect between a first semiconductor die of the stack of semiconductor dies and each other semiconductor dies in the stack of semiconductor dies, the first through-stack interconnect extending through a first portion of the stack of semiconductor dies; determining resistances of a second through-stack interconnect between the first semiconductor die and each other semiconductor dies in the stack of semiconductor dies, the second through-stack interconnect extending through a second portion of the stack of semiconductor dies; when each of the determined resistances of the first through-stack interconnect and the determined resistances of the second through-stack interconnect is above a threshold magnitude, determining that all of a plurality of third through-stack interconnects are electrically connected, the plurality of third through-stack interconnects extending through a third portion of the stack of semiconductor dies; and when at least one of the determined resistances of the first through-stack interconnect or the determined resistances of the second through-stack interconnect is below the threshold magnitude, determining that at least a portion of the third through-stack interconnects are electrically disconnected.
 18. The method of claim 17, wherein the first portion and the second portions of the stack of semiconductor dies are more prone to connectivity defects than the third portion of the stack of semiconductor dies.
 19. The method of claim 17, wherein the first portion and the second portions of the stack of semiconductor dies are more prone to warpage than the third portion of the stack of semiconductor dies.
 20. The method of claim 17, wherein the first portion of the stack of semiconductor dies is a first edge portion of the stack of semiconductor dies, wherein the second portion of the stack of semiconductor dies is a second edge portion of the stack of semiconductor dies, and wherein the third portion of the stack of semiconductor dies is laterally inboard of the first portion and the second portions. 